The present invention relates to the fluid pumping and filtration arts. It finds particular application in conjunction with a top-flow centrifugal fluid pump for use in pumping highly-corrosive fluids, such as used in a semi-conductor etching system, and will be described with particular reference thereto. However, it should be appreciated that the present invention may also find application in conjunction with other systems and applications where the pumping and/or filtration of fluids is performed.
FIG. 1 illustrates an exemplary impeller-type fluid pump and filtration unit A for a semi-conductor etching system. The pump and filtration unit is disclosed in commonly-owned U.S. Pat. No. 5,021,151, which is hereby incorporated by reference for all that it teaches.
Briefly, the pump and filtration unit A includes a housing 10 having a pump chamber 12 and a filter chamber 14 spaced apart from the pump chamber. The pump and filter chambers 12, 14 communicate through an intermediate passageway or bore 16. An inlet port 18 of the housing communicates with an inlet 20 of the pump chamber. An outlet port 22 of the housing communicates with an outlet 24 of the filter chamber. A centrifugal-type fluid pump within the housing 10 includes an impeller 26 positioned within the pump chamber 12. A hollow impeller shaft sleeve 28 is secured to the impeller and extends through a bore 30 in the housing. A drive motor assembly 32 is secured to the housing by an adapter plate 34. An output shaft 36 of the drive motor extends through the adapter plate 34 and impeller shaft sleeve 28 and is secured to the impeller 26. A replaceable filter element 38 is located within the filter chamber 14.
The impeller 26 is formed from a first section 40 and a second section 42, each of which has a plurality of impeller vanes associated therewith. In particular, the impeller vanes 44 associated with first impeller section 40 draw fluid from the inlet port 20 to the pump chamber 12 in a direction toward the drive motor assembly 32. The impeller vanes 46 associated with the second impeller section 42 move fluid more efficiently than the impeller vanes 44 associated with the first section 40. As a result, a positive suction force is created by the impeller vanes 46 to prevent fluid from being pushed up into the bore 30 and potentially reaching the drive motor unit 32.
In operation, the pump and filtration unit A is located in a tank or tub together with a weir basket that holds microelectronic circuits or chips. The tub contains a corrosive chemical solution or fluid (e.g. corrosive acid(s) heated to 160-180xc2x0 C.) which overflows the top of the basket and engulfs the unit A, and which is intended to etch the microelectronic circuits or chips. When the pump and filtration unit A is energized, the corrosive fluid is drawn from the inlet port 16 to the pump chamber 12 by the impeller 26. The impeller then pumps the fluid into the filtration chamber 14 and through the filter 38 before being discharged back into the tub at the outlet 22. Notwithstanding the positive suction force generated by the second impeller section 42, a seal assembly 48 (FIG. 2) such as a labyrinth seal assembly further prevents corrosive fluid from flowing between the shaft sleeve 38 and the adapter plate 34 to the drive motor assembly 32.
It should be appreciated that the drive motor assembly provides a very efficient means of pumping fluids when coupled to the centrifugal-type pump. High rotational speeds of the centrifugal-type pump 26 can produce high fluid-flow rates at moderate outlet pressures. However, when the outlet pressure increases (such as when the filter 38 becomes at least partially blocked with particles generated by the etching process), the fluid flow drops off sharply beyond the design parameters of the pump. In the most extreme case when the pump is xe2x80x9cdead headedxe2x80x9d (i.e. outlet 22 and/or 24 is blocked completely), the pressure created by the first impeller section 40 can force the corrosive fluid up the bore 30, past the seal assembly 48, and into the drive motor assembly 32. When pumping aggressive (i.e. highly-corrosive) fluids, this can result in the premature failure of the drive motor and/or the drive bearings.
Accordingly, it has been considered desirable to develop a new and improved top-flow centrifugal fluid pump for use in pumping corrosive fluids, which pump meets the above-stated needs and overcomes the foregoing difficulties and others while providing better and more advantageous results.
The present invention is directed to a fluid pump that is made from a high-purity fluroplastic material. The pump is used to circulate extremely corrosive fluids that are heated to temperatures of 160-180xc2x0 C. through at least one filtration unit. The pump can be used in a semiconductor etching system. The pump utilizes the driven side of an impeller to generate a suction force that draws the corrosive fluid into a pumping chamber from at least one inlet port.
A pedestal support or shaft sleeve, through which a motor drive shaft extends, is modified to create an annular passageway that permits the corrosive fluid to enter the pumping chamber from the inlet. With the inlet design of the present invention, a drive motor seal assembly is no longer subjected to corrosive fluid because the seal assembly is positioned on the suction side of the impeller. In a xe2x80x9cdead headedxe2x80x9d condition the corrosive fluid flow stops completely as the fluid within the pumping chamber simply remains in shear.
Thus, in one aspect of the present invention a fluid pump is disclosed. The fluid pump includes a housing defining a pump chamber; a single fluid inlet communicating with the pump chamber; an impeller positioned within the pump chamber; and a drive shaft extending through the fluid inlet and coupled to the impeller.
In a second aspect of the present invention, a corrosive fluid pumping system including a tub adapted to hold a corrosive fluid and a fluid pump is disclosed. The fluid pump includes a housing defining a pump chamber; a single fluid inlet communicating with the pump chamber; an impeller positioned within the pump chamber; and a drive shaft extending through the fluid inlet and coupled to the impeller.
Accordingly, one advantage of the present invention is the provision of a fluid pump that prevents corrosive fluid from reaching a drive motor unit during a worst-case, xe2x80x9cdead-headedxe2x80x9d operating condition of the fluid pump.
Another advantage of the present invention is the provision of a fluid pump having at least one inlet port positioned intermediate a pumping chamber and a drive motor housing.
Yet another advantage of the present invention is the provision of a fluid pump having an impeller that draws fluid into a pumping chamber in a direction away from a drive motor housing.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.